/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2010 Neil C Smith.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 3 only, as
 * published by the Free Software Foundation.
 * 
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 3 for more details.
 * 
 * You should have received a copy of the GNU General Public License version 3
 * along with this work; if not, see http://www.gnu.org/licenses/
 * 
 * 
 * Please visit http://neilcsmith.net if you need additional information or
 * have any questions.
 *
 */

package net.neilcsmith.praxis.util.interpolation;

/**
 *
 * @author Neil C Smith
 */
public class ExponentialInterpolator implements Interpolator {

    private final static ExponentialInterpolator instance = new ExponentialInterpolator();

    private final double Em1 = Math.E - 1;


    private ExponentialInterpolator() {}

    public double interpolate(double value) {
        if (value <= 0) {
            return 0;
        } else if (value >= 1) {
            return 1;
        } else {
//            return Math.log1p(value * Em1);
            return Math.expm1(value) / Em1;
        }
    }

    public double reverseInterpolate(double value) {
        if (value <= 0) {
            return 0;
        } else if (value >= 1) {
            return 1;
        } else {
//            return Math.expm1(value) / Em1;
            return Math.log1p(value * Em1);
        }
    }

    public static ExponentialInterpolator getInstance() {
        return instance;
    }

}
